The control of synthesis of herpes simplex virus (HSV) specific mRNA is being studied. We have developed techniques for the isolation, mapping, and in vitro translation of HSV-1 mRNA species. This supplemental request is aimed at maximizing our progress. Specific areas to be studied are: (1) The localization and direction of transcription of HSV-1 mRNA species; (2) detailed analysis of the structure of specific HSV-1 mRNA species; (3) study of the nuclear precursors of HSV-1 mRNA; (4) examination of the biological activity of HSV-1 transcripts. Methods to be used include preparative hybridization of HSV-1 mRNA using viral DNA and restriction fragment bound to cellulose; study of possible interruption of mRNA sequences using S1 nuclease digestion; use of reverse transcriptase to make 3' cDNA probes to HSV-1 mRNA; electron microscopy of DNA-RNA hybrids; and various assays of biological activity.